Quantitative detection of microcystin-LR in Bellamya aeruginosa by thin-layer chromatography coupled with surface-enhanced Raman spectroscopy based on in-situ ZIF-67/Ag NPs/Au NWs composite substrate.

As a hypertoxic natural toxin, the risk of Microcystin-leucine-arginine (MC-LR) residues in Bellamya aeruginosa deserves more attention. Herein, employing the conventional thin-layer chromatography (TLC) technology and a novel surface-enhanced Raman scattering (SERS) substrate, a TLC-SERS chip was fabricated for the purification and quantitative detection of MC-LR in complex samples. The substrate exhibited excellent SERS performance with an enhancement factor of 6.6 × 107, a low detection limit of 2.27 × 10-9 mM for MC-LR, excellent uniformity and reproducibility, as well as a wide linear range. With the application of TLC, the MC-LR was efficiently purified and the concentration was increased to >3 times. Ultimately, recovery rates fluctuated between 93.28% and 101.66% were obtained from the TLC-SERS chip. On balance, the TLC-SERS chip has a robust capacity for achieving rapid and stable quantitative detection of MC-LR, which promises to improve the efficiency of food safety monitoring.

2 Year Wencheng Waxy Yam Pesticide Residue Investigation and Quality Evaluation.

Wencheng waxy yam is famous for its glutinous and resilient taste, similar to waxy rice, but there is currently a lack of systematic research on the quality of this featured product, and little is known about its pesticide residues. We carried out a 2 year investigation of Wencheng waxy yam at seven sites from 2021 to 2022 to determine the oxidase content and phytochemical characteristics, namely, amylose, amylopectin, protein, reducing sugar, and mineral contents, such as K, Fe, and Zn, including the status of pesticide residues. The results showed that the oxidase content was affected by rainfall, and adequate water reduced the production of oxidase, including polyphenol oxidase, peroxidase, and superoxide dismutase, during the late growth stage of waxy yam, which was beneficial for reducing browning in yam processing. Radar map analysis showed that, with comprehensive evaluation, standardized production sites 1 and 2 had a relatively higher quality than 3-7 with small farmers. The results of pesticide multiresidue testing showed that no pesticides were detected in 64.29% of the samples, and the detected residues in the samples were very low, making the consumption of yam safe for consumers. These findings could be beneficial for the exploitation of the health benefits of waxy yam tubers and the innovation of yam-based functional products.

Comparison of gelling properties and flow behaviors of microbial transglutaminase (MTGase) and pectin modified fish gelatin.

The gelling and structural properties of microbial transglutaminase (MTGase) and pectin modified fish gelatin were compared to investigate their performances on altering fish gelatin properties. Our results showed that within a certain concentration, both MTGase and pectin had positive effects on the gelation point, melting point, gel strength, textural, and swelling properties of fish gelatin. Particularly, low pectin content (0.5%, w/v) could give fish gelatin gels the highest values of gel strength, melting temperature, and hardness. Meantime, flow behavior results showed that both MTGase and pectin could increase fish gelatin viscosity without changing its fluid characteristic, but the latter gave fish gelatin higher viscosity. Both MTGase and pectin could increase the lightness of fish gelatin gels but decreases its transparency. More importantly, fluorescence and UV absorbance spectra, particle size distribution, and confocal microscopy results indicated that MTGase and pectin could change the structure of fish gelatin with the formation of large aggregates. Compared with MTGae modified fish gelatin, pectin could endow fish gelatin had similar gel strength, thermal and textural properties to pig skin gelatin.

Effects of electron beam irradiation on the biochemical properties and structure of myofibrillar protein from Tegillarca granosa meat.

The effect of electron beam irradiation at doses of 0-9 kGy on the biochemical properties and structure of myofibrillar protein from Tegillarca granosa (T. granosa) was investigated. There was no effect of irradiation on the surface hydrophobicity of the myofibrillar protein, however total sulfhydryl content and Ca2+-ATPase activity both declined to varying extents with increasing irradiation dose. Irradiation also affected the composition of the myofibrillar protein; with increasing dose of irradiation, the actin, paramyosin and myosin heavy chain contents of the myofibrillar protein were partially degraded. Irradiation reduced the α-helix content and increased the ß-sheet content but these effects were less dependent on the dose of irradiation. The 'hardness', 'gumminess', 'chewiness' and 'resilience' of T. granosa meat were improved at irradiation doses of 3-5 kGy. Collectively, our results support an optimum irradiation dose of 3-5 kGy for the preservation of T. granosa meat.

[Preparation of oligosaccharides from alginate by fermenting combined with membrane separation method and analysis of the oligomers].

Changes in biomass, oligosaccharides content and alginate lyase activity in broth of Alteromonas sp. incubated in shaking flask and fermentation jar were studied. According to those changes, parameters were established for preparing oligosaccharides from alginate by fermentation combined with nano-filtration membrane separation method. Resulting oligosaccharides were analyzed by gel permeation chromatography and thin layer chromatography. One liter culture medium(pH 7.5) contains 5 g yeast extract, l0 g peptone, 0.1 g FeSO4, 12 g sodium alginate and 1.5 g NaCl. When incubating at 28 degrees C, the result showed that the optimal fermentation time was 30 h to obtain the highest production of oligosaccharides in the broth. After ultra-filtration and nano-filtration, 94.0% of the total oligosaccharides was recovered from the broth, and meanwhile 93.3% of the salt was removed. Gel permeation chromatography and TLC analyses indicated that the resulting oligosaccharides were composed of five fractions with different degree of polymerization.

Kinetics of picosecond laser pulse induced charge separation and proton transfer in bacteriorhodopsin.

Bacteriorhodopsin (BR) films oriented by an electrophoretic method are deposited on a transparent conductive ITO glass. A counterelectrode of copper and gelose gel is used to compose a sandwich-type photodetector with the structure of ITO/BR film/gelose gel/Cu. A single 30-ps laser pulse and a mode-locked pulse train are respectively used to excite the BR photodetector. The ultrafast falling edge and the bipolar response signal are measured by the digital oscilloscope under seven different time ranges. Marquardt nonlinear least squares fitting is used to fit all the experimental data and a good fitting equation is found to describe the kinetic process of the photoelectric signal. Data fitting resolves six exponential components that can be assigned to a seven-step BR photocycle model: BR-->K-->KL-->L-->M-->N-->O-->BR. Comparing tests of the BR photodetector with a 100-ps Si PIN photodiode demonstrates that this type of BR photodetector has at least 100-ps response time and can also serve as a fast photoelectric switch.